DevTools: Rename WebInspector.DOMAgent into WebInspector.DOMModel

LayoutTests/inspector/elements/perform-undo-undo.html

Index: LayoutTests/inspector/elements/perform-undo-undo.html
diff --git a/LayoutTests/inspector/elements/perform-undo-undo.html b/LayoutTests/inspector/elements/perform-undo-undo.html
index 3b701b2f3f4ed31ca0f13cd9d9dba18469831b06..b83b56e36b7feb53cb98bf1af589a0c8ffb2f7fb 100644
--- a/LayoutTests/inspector/elements/perform-undo-undo.html
+++ b/LayoutTests/inspector/elements/perform-undo-undo.html
@@ -36,7 +36,7 @@ function test()
             InspectorTest.dumpElementsTree(containerNode);
             step4();
         }
-        WebInspector.domAgent.undo(callback);
+        WebInspector.domModel.undo(callback);
     }
 
     function step4()
@@ -47,7 +47,7 @@ function test()
             InspectorTest.dumpElementsTree(containerNode);
             InspectorTest.completeTest();
         }
-        WebInspector.domAgent.undo(callback);
+        WebInspector.domModel.undo(callback);
     }
 }